import java.util.*;
public class Main{
    public static void main(String[] args){
        long[] f = new long[91];
        f[0] = 1;
        f[1] = 1;
        for(int i = 2; i <= 90; ++i){
            f[i] = f[i-1] + f[i-2];
        }
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            System.out.println(f[sc.nextInt()]);
        }
    }
}